Tubeless is decidedly easier to fix a simple puncture. You plug and go. You carry a plug kit and a small pump/CO2.
With tubes, you have to dismount the wheel, break the bead, dismount the tire, repair/replace the tube, and put it all back together. You have to carry all the tools necessary to dismount either wheel, tire irons, a pump, and spare tube(s) or a tube patching kit. I just had a friend how had a rear puncture on this 640 KTM in the rain on the side of the interstate. He was there with trucks trundling by a few feet away for nearly two hours. While it can be done, it is not pleasant.
A further advantage of tubeless is that they run cooler and are safer. And they're much LESS likely to de-bead after a flat. If you have a sudden puncture on a tubed tire and it de-beads, your chance of going down are pretty high.
All this being said, there are some advantages to tubes in hard-core dirt-bike terrain. If you have the tools and skills, you can fix almost any type of puncture by replacing the tube, but there are types of punctures you might encounter in rocky terrain (rips, tears, slashes, etc.) that are not amenable to plugs. This is why the super-prepared, heavy-duty off-road adventurer may carry tubes for their tubeless wheels - as a last ditch way to get the tire to hold air and get them home.
Bottom line is that tubeless is safer and much more suitable for a long-distance, high-speed bike that is mostly going to see pavement and light dirt and where any puncture is likely to be something simple like a nail or screw. Exactly the sort of riding that is in the S10's wheelhouse. Tubed might be better if your dirt riding is truly hard-core in very rocky terrain with low tire pressures and you're willing to carry all the tools and know how to use them.
While I admire the workmanship and engineering behind the effort to put a 21" on the front of the S10, my initial reaction is "Why not just get a KTM990 to begin with..." rather than attempting to push a S10 into doing something it was never really designed to do. Sorry to say this to the S10 worshippers, but for hard-core dirt riding, the KTM is a much better bike than the S10 can ever be - its chain drive,, 75+ lbs lighter, and has suspension travel and ground clearance that the S10 can only dream about. And the conversion to tubed wheels would be a huge sacrifice in my book. All this being said, if you absolutely have no choice but to make your S10 work better in the dirt, the 21" front end will help quite a bit.
Just my $0.02.
- Mark